The present invention relates to a method and apparatus for making molten steel from solid iron sources.
Molten steel can be made from solid iron sources, such as scrap iron, scrap steel, solid crude iron, sponge iron and mixtures of such materials, by a process which comprises melting and simultaneously or subsequently refining the source materials. For economy it is particularly important that the melting heat be supplied with an optimum efficiency to the solid iron sources to be melted and/or the metal bath used for melting. It is known to supply the melting heat by feeding electrical energy into the molten bath or by burning carbon with oxygen in the molten bath. To refine the carbon-containing molten material to a carbon content below 0.4% by weight, oxygen or oxygen-enriched air is blown into or onto the molten material. Refining may be effected after or during the melting operation.
Published German Patent Application 3,735,150 discloses a process of supplying thermal energy to molten metal. In that process solid carbon and solid metallic materials, preferably scrap steel, which are to be melted, are fed to the melting vessel and oxygen is blown through submerged nozzles into the molten material which has remained in the melting vessel or into molten metal which is being charged into the melting vessel. In that known process it is contemplated to charge carbon in the form of sheet metal-sheathed coal briquettes. Published German Patent Application 3,045,966 discloses a process of refining molten metal, particularly liquid hot metal, in an open-hearth furnace, in an electric arc furnace, or in a converter by an oxygen-containing gas which is fed into the bath below its surface. The oxygen-containing gas is fed through nozzles, which consist of a plurality of concentric tubes. An oxygen-containing gas is conducted through the central tube and a protecting fluid is conducted through the first concentric tube and consists of a gaseous or liquid hydrocarbon or of water or of organic hydroxyl compounds.
In all known processes the melting heat supplied to the melting vessel is utilized only with an inadequate efficiency so that melting, particularly of large quantities of scrap, within a predetermined time is difficult to achieve.